Study and control of the alignment of the SILHI beam

The low energy line of the IPHI injector includes 2 couples of magnetic deflectors operating in 2 transverse directions. This work aims at assessing the capacity of these deflectors to collimate efficiently the beam in the RFQ (radio-frequency quadrupole) inlet. There are 4 main causes of mis-alignment : first, the misalignment of the line components such as the ECR source or the 2 solenoids; second, the earth magnetic field; third the non-linear and non-axisymmetric forces due to charge distribution inside the beam tend to break the beam's circular symmetry; and four, particle losses tend to shift the centre of mass of the beam. It appears that the power of the deflectors is sufficient, in the SILHI present scheme, to center the beam at the interface with RFQ. Moving away the 2 deflectors from each other will improve their efficiency. The alignment procedures are complex: setting first the solenoid fields before the deflectors' could make the task easier but an advanced automated algorithm seems necessary. (A.C.)